src/runtime/os1_linux.go - go - Git at Google

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package runtime

 import "unsafe"

 var sigset_all sigset = sigset{^uint32(0), ^uint32(0)}

 // Linux futex.
 //
 //	futexsleep(uint32 *addr, uint32 val)
 //	futexwakeup(uint32 *addr)
 //
 // Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
 // Futexwakeup wakes up threads sleeping on addr.
 // Futexsleep is allowed to wake up spuriously.

 const (
 	_FUTEX_WAIT = 0
 	_FUTEX_WAKE = 1
 )

 // Atomically,
 //	if(*addr == val) sleep
 // Might be woken up spuriously; that's allowed.
 // Don't sleep longer than ns; ns < 0 means forever.
 //go:nosplit
 func futexsleep(addr *uint32, val uint32, ns int64) {
 	var ts timespec

 	// Some Linux kernels have a bug where futex of
 	// FUTEX_WAIT returns an internal error code
 	// as an errno.  Libpthread ignores the return value
 	// here, and so can we: as it says a few lines up,
 	// spurious wakeups are allowed.
 	if ns < 0 {
 		futex(unsafe.Pointer(addr), _FUTEX_WAIT, val, nil, nil, 0)
 		return
 	}

 	// It's difficult to live within the no-split stack limits here.
 	// On ARM and 386, a 64-bit divide invokes a general software routine
 	// that needs more stack than we can afford. So we use timediv instead.
 	// But on real 64-bit systems, where words are larger but the stack limit
 	// is not, even timediv is too heavy, and we really need to use just an
 	// ordinary machine instruction.
 	if ptrSize == 8 {
 		ts.set_sec(ns / 1000000000)
 		ts.set_nsec(int32(ns % 1000000000))
 	} else {
 		ts.tv_nsec = 0
 		ts.set_sec(int64(timediv(ns, 1000000000, (*int32)(unsafe.Pointer(&ts.tv_nsec)))))
 	}
 	futex(unsafe.Pointer(addr), _FUTEX_WAIT, val, unsafe.Pointer(&ts), nil, 0)
 }

 // If any procs are sleeping on addr, wake up at most cnt.
 //go:nosplit
 func futexwakeup(addr *uint32, cnt uint32) {
 	ret := futex(unsafe.Pointer(addr), _FUTEX_WAKE, cnt, nil, nil, 0)
 	if ret >= 0 {
 		return
 	}

 	// I don't know that futex wakeup can return
 	// EAGAIN or EINTR, but if it does, it would be
 	// safe to loop and call futex again.
 	systemstack(func() {
 		print("futexwakeup addr=", addr, " returned ", ret, "\n")
 	})

 	*(*int32)(unsafe.Pointer(uintptr(0x1006))) = 0x1006
 }

 func getproccount() int32 {
 	var buf [16]uintptr
 	r := sched_getaffinity(0, unsafe.Sizeof(buf), &buf[0])
 	n := int32(0)
 	for _, v := range buf[:r/ptrSize] {
 		for i := 0; i < 64; i++ {
 			n += int32(v & 1)
 			v >>= 1
 		}
 	}
 	if n == 0 {
 		n = 1
 	}
 	return n
 }

 // Clone, the Linux rfork.
 const (
 	_CLONE_VM             = 0x100
 	_CLONE_FS             = 0x200
 	_CLONE_FILES          = 0x400
 	_CLONE_SIGHAND        = 0x800
 	_CLONE_PTRACE         = 0x2000
 	_CLONE_VFORK          = 0x4000
 	_CLONE_PARENT         = 0x8000
 	_CLONE_THREAD         = 0x10000
 	_CLONE_NEWNS          = 0x20000
 	_CLONE_SYSVSEM        = 0x40000
 	_CLONE_SETTLS         = 0x80000
 	_CLONE_PARENT_SETTID  = 0x100000
 	_CLONE_CHILD_CLEARTID = 0x200000
 	_CLONE_UNTRACED       = 0x800000
 	_CLONE_CHILD_SETTID   = 0x1000000
 	_CLONE_STOPPED        = 0x2000000
 	_CLONE_NEWUTS         = 0x4000000
 	_CLONE_NEWIPC         = 0x8000000

 	cloneFlags = _CLONE_VM | /* share memory */
 		_CLONE_FS | /* share cwd, etc */
 		_CLONE_FILES | /* share fd table */
 		_CLONE_SIGHAND | /* share sig handler table */
 		_CLONE_THREAD /* revisit - okay for now */
 )

 // May run with m.p==nil, so write barriers are not allowed.
 //go:nowritebarrier
 func newosproc(mp *m, stk unsafe.Pointer) {
 	/*
 	 * note: strace gets confused if we use CLONE_PTRACE here.
 	 */
 	mp.tls[0] = uintptr(mp.id) // so 386 asm can find it
 	if false {
 		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " clone=", funcPC(clone), " id=", mp.id, "/", mp.tls[0], " ostk=", &mp, "\n")
 	}

 	// Disable signals during clone, so that the new thread starts
 	// with signals disabled.  It will enable them in minit.
 	var oset sigset
 	rtsigprocmask(_SIG_SETMASK, &sigset_all, &oset, int32(unsafe.Sizeof(oset)))
 	ret := clone(cloneFlags, stk, unsafe.Pointer(mp), unsafe.Pointer(mp.g0), unsafe.Pointer(funcPC(mstart)))
 	rtsigprocmask(_SIG_SETMASK, &oset, nil, int32(unsafe.Sizeof(oset)))

 	if ret < 0 {
 		print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", -ret, ")\n")
 		throw("newosproc")
 	}
 }

 // Version of newosproc that doesn't require a valid G.
 //go:nosplit
 func newosproc0(stacksize uintptr, fn unsafe.Pointer) {
 	stack := sysAlloc(stacksize, &memstats.stacks_sys)
 	if stack == nil {
 		write(2, unsafe.Pointer(&failallocatestack[0]), int32(len(failallocatestack)))
 		exit(1)
 	}
 	ret := clone(cloneFlags, unsafe.Pointer(uintptr(stack)+stacksize), nil, nil, fn)
 	if ret < 0 {
 		write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
 		exit(1)
 	}
 }

 var failallocatestack = []byte("runtime: failed to allocate stack for the new OS thread\n")
 var failthreadcreate = []byte("runtime: failed to create new OS thread\n")

 func osinit() {
 	ncpu = getproccount()
 }

 var urandom_dev = []byte("/dev/urandom\x00")

 func getRandomData(r []byte) {
 	if startupRandomData != nil {
 		n := copy(r, startupRandomData)
 		extendRandom(r, n)
 		return
 	}
 	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
 	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
 	closefd(fd)
 	extendRandom(r, int(n))
 }

 func goenvs() {
 	goenvs_unix()
 }

 // Called to initialize a new m (including the bootstrap m).
 // Called on the parent thread (main thread in case of bootstrap), can allocate memory.
 func mpreinit(mp *m) {
 	mp.gsignal = malg(32 * 1024) // Linux wants >= 2K
 	mp.gsignal.m = mp
 }

 func msigsave(mp *m) {
 	smask := (*sigset)(unsafe.Pointer(&mp.sigmask))
 	if unsafe.Sizeof(*smask) > unsafe.Sizeof(mp.sigmask) {
 		throw("insufficient storage for signal mask")
 	}
 	rtsigprocmask(_SIG_SETMASK, nil, smask, int32(unsafe.Sizeof(*smask)))
 }

 // Called to initialize a new m (including the bootstrap m).
 // Called on the new thread, can not allocate memory.
 func minit() {
 	// Initialize signal handling.
 	_g_ := getg()
 	signalstack((*byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 32*1024)

 	// restore signal mask from m.sigmask and unblock essential signals
 	nmask := *(*sigset)(unsafe.Pointer(&_g_.m.sigmask))
 	for i := range sigtable {
 		if sigtable[i].flags&_SigUnblock != 0 {
 			nmask[(i-1)/32] &^= 1 << ((uint32(i) - 1) & 31)
 		}
 	}
 	rtsigprocmask(_SIG_SETMASK, &nmask, nil, int32(unsafe.Sizeof(nmask)))
 }

 // Called from dropm to undo the effect of an minit.
 func unminit() {
 	_g_ := getg()
 	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
 	rtsigprocmask(_SIG_SETMASK, smask, nil, int32(unsafe.Sizeof(*smask)))
 	signalstack(nil, 0)
 }

 func memlimit() uintptr {
 	/*
 		TODO: Convert to Go when something actually uses the result.

 		Rlimit rl;
 		extern byte runtime·text[], runtime·end[];
 		uintptr used;

 		if(runtime·getrlimit(RLIMIT_AS, &rl) != 0)
 			return 0;
 		if(rl.rlim_cur >= 0x7fffffff)
 			return 0;

 		// Estimate our VM footprint excluding the heap.
 		// Not an exact science: use size of binary plus
 		// some room for thread stacks.
 		used = runtime·end - runtime·text + (64<<20);
 		if(used >= rl.rlim_cur)
 			return 0;

 		// If there's not at least 16 MB left, we're probably
 		// not going to be able to do much.  Treat as no limit.
 		rl.rlim_cur -= used;
 		if(rl.rlim_cur < (16<<20))
 			return 0;

 		return rl.rlim_cur - used;
 	*/

 	return 0
 }

 //#ifdef GOARCH_386
 //#define sa_handler k_sa_handler
 //#endif

 func sigreturn()
 func sigtramp()

 func setsig(i int32, fn uintptr, restart bool) {
 	var sa sigactiont
 	memclr(unsafe.Pointer(&sa), unsafe.Sizeof(sa))
 	sa.sa_flags = _SA_SIGINFO | _SA_ONSTACK | _SA_RESTORER
 	if restart {
 		sa.sa_flags |= _SA_RESTART
 	}
 	sa.sa_mask = ^uint64(0)
 	// Although Linux manpage says "sa_restorer element is obsolete and
 	// should not be used". x86_64 kernel requires it. Only use it on
 	// x86.
 	if GOARCH == "386" || GOARCH == "amd64" {
 		sa.sa_restorer = funcPC(sigreturn)
 	}
 	if fn == funcPC(sighandler) {
 		fn = funcPC(sigtramp)
 	}
 	sa.sa_handler = fn
 	if rt_sigaction(uintptr(i), &sa, nil, unsafe.Sizeof(sa.sa_mask)) != 0 {
 		throw("rt_sigaction failure")
 	}
 }

 func setsigstack(i int32) {
 	var sa sigactiont
 	if rt_sigaction(uintptr(i), nil, &sa, unsafe.Sizeof(sa.sa_mask)) != 0 {
 		throw("rt_sigaction failure")
 	}
 	if sa.sa_handler == 0 || sa.sa_handler == _SIG_DFL || sa.sa_handler == _SIG_IGN || sa.sa_flags&_SA_ONSTACK != 0 {
 		return
 	}
 	sa.sa_flags |= _SA_ONSTACK
 	if rt_sigaction(uintptr(i), &sa, nil, unsafe.Sizeof(sa.sa_mask)) != 0 {
 		throw("rt_sigaction failure")
 	}
 }

 func getsig(i int32) uintptr {
 	var sa sigactiont

 	memclr(unsafe.Pointer(&sa), unsafe.Sizeof(sa))
 	if rt_sigaction(uintptr(i), nil, &sa, unsafe.Sizeof(sa.sa_mask)) != 0 {
 		throw("rt_sigaction read failure")
 	}
 	if sa.sa_handler == funcPC(sigtramp) {
 		return funcPC(sighandler)
 	}
 	return sa.sa_handler
 }

 func signalstack(p *byte, n int32) {
 	var st sigaltstackt
 	st.ss_sp = p
 	st.ss_size = uintptr(n)
 	st.ss_flags = 0
 	if p == nil {
 		st.ss_flags = _SS_DISABLE
 	}
 	sigaltstack(&st, nil)
 }

 func updatesigmask(m sigmask) {
 	var mask sigset
 	copy(mask[:], m[:])
 	rtsigprocmask(_SIG_SETMASK, &mask, nil, int32(unsafe.Sizeof(mask)))
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package runtime

	import "unsafe"

	var sigset_all sigset = sigset{^uint32(0), ^uint32(0)}

	// Linux futex.
	//
	// futexsleep(uint32 *addr, uint32 val)
	// futexwakeup(uint32 *addr)
	//
	// Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
	// Futexwakeup wakes up threads sleeping on addr.
	// Futexsleep is allowed to wake up spuriously.

	const (
	_FUTEX_WAIT = 0
	_FUTEX_WAKE = 1
	)

	// Atomically,
	// if(*addr == val) sleep
	// Might be woken up spuriously; that's allowed.
	// Don't sleep longer than ns; ns < 0 means forever.
	//go:nosplit
	func futexsleep(addr *uint32, val uint32, ns int64) {
	var ts timespec

	// Some Linux kernels have a bug where futex of
	// FUTEX_WAIT returns an internal error code
	// as an errno. Libpthread ignores the return value
	// here, and so can we: as it says a few lines up,
	// spurious wakeups are allowed.
	if ns < 0 {
	futex(unsafe.Pointer(addr), _FUTEX_WAIT, val, nil, nil, 0)
	return
	}

	// It's difficult to live within the no-split stack limits here.
	// On ARM and 386, a 64-bit divide invokes a general software routine
	// that needs more stack than we can afford. So we use timediv instead.
	// But on real 64-bit systems, where words are larger but the stack limit
	// is not, even timediv is too heavy, and we really need to use just an
	// ordinary machine instruction.
	if ptrSize == 8 {
	ts.set_sec(ns / 1000000000)
	ts.set_nsec(int32(ns % 1000000000))
	} else {
	ts.tv_nsec = 0
	ts.set_sec(int64(timediv(ns, 1000000000, (*int32)(unsafe.Pointer(&ts.tv_nsec)))))
	}
	futex(unsafe.Pointer(addr), _FUTEX_WAIT, val, unsafe.Pointer(&ts), nil, 0)
	}

	// If any procs are sleeping on addr, wake up at most cnt.
	//go:nosplit
	func futexwakeup(addr *uint32, cnt uint32) {
	ret := futex(unsafe.Pointer(addr), _FUTEX_WAKE, cnt, nil, nil, 0)
	if ret >= 0 {
	return
	}

	// I don't know that futex wakeup can return
	// EAGAIN or EINTR, but if it does, it would be
	// safe to loop and call futex again.
	systemstack(func() {
	print("futexwakeup addr=", addr, " returned ", ret, "\n")
	})

	(int32)(unsafe.Pointer(uintptr(0x1006))) = 0x1006
	}

	func getproccount() int32 {
	var buf [16]uintptr
	r := sched_getaffinity(0, unsafe.Sizeof(buf), &buf[0])
	n := int32(0)
	for _, v := range buf[:r/ptrSize] {
	for i := 0; i < 64; i++ {
	n += int32(v & 1)
	v >>= 1
	}
	}
	if n == 0 {
	n = 1
	}
	return n
	}

	// Clone, the Linux rfork.
	const (
	_CLONE_VM = 0x100
	_CLONE_FS = 0x200
	_CLONE_FILES = 0x400
	_CLONE_SIGHAND = 0x800
	_CLONE_PTRACE = 0x2000
	_CLONE_VFORK = 0x4000
	_CLONE_PARENT = 0x8000
	_CLONE_THREAD = 0x10000
	_CLONE_NEWNS = 0x20000
	_CLONE_SYSVSEM = 0x40000
	_CLONE_SETTLS = 0x80000
	_CLONE_PARENT_SETTID = 0x100000
	_CLONE_CHILD_CLEARTID = 0x200000
	_CLONE_UNTRACED = 0x800000
	_CLONE_CHILD_SETTID = 0x1000000
	_CLONE_STOPPED = 0x2000000
	_CLONE_NEWUTS = 0x4000000
	_CLONE_NEWIPC = 0x8000000

	cloneFlags = _CLONE_VM \| /* share memory */
	_CLONE_FS \| /* share cwd, etc */
	_CLONE_FILES \| /* share fd table */
	_CLONE_SIGHAND \| /* share sig handler table */
	_CLONE_THREAD /* revisit - okay for now */
	)

	// May run with m.p==nil, so write barriers are not allowed.
	//go:nowritebarrier
	func newosproc(mp *m, stk unsafe.Pointer) {
	/*
	* note: strace gets confused if we use CLONE_PTRACE here.
	*/
	mp.tls[0] = uintptr(mp.id) // so 386 asm can find it
	if false {
	print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " clone=", funcPC(clone), " id=", mp.id, "/", mp.tls[0], " ostk=", &mp, "\n")
	}

	// Disable signals during clone, so that the new thread starts
	// with signals disabled. It will enable them in minit.
	var oset sigset
	rtsigprocmask(_SIG_SETMASK, &sigset_all, &oset, int32(unsafe.Sizeof(oset)))
	ret := clone(cloneFlags, stk, unsafe.Pointer(mp), unsafe.Pointer(mp.g0), unsafe.Pointer(funcPC(mstart)))
	rtsigprocmask(_SIG_SETMASK, &oset, nil, int32(unsafe.Sizeof(oset)))

	if ret < 0 {
	print("runtime: failed to create new OS thread (have ", mcount(), " already; errno=", -ret, ")\n")
	throw("newosproc")
	}
	}

	// Version of newosproc that doesn't require a valid G.
	//go:nosplit
	func newosproc0(stacksize uintptr, fn unsafe.Pointer) {
	stack := sysAlloc(stacksize, &memstats.stacks_sys)
	if stack == nil {
	write(2, unsafe.Pointer(&failallocatestack[0]), int32(len(failallocatestack)))
	exit(1)
	}
	ret := clone(cloneFlags, unsafe.Pointer(uintptr(stack)+stacksize), nil, nil, fn)
	if ret < 0 {
	write(2, unsafe.Pointer(&failthreadcreate[0]), int32(len(failthreadcreate)))
	exit(1)
	}
	}

	var failallocatestack = []byte("runtime: failed to allocate stack for the new OS thread\n")
	var failthreadcreate = []byte("runtime: failed to create new OS thread\n")

	func osinit() {
	ncpu = getproccount()
	}

	var urandom_dev = []byte("/dev/urandom\x00")

	func getRandomData(r []byte) {
	if startupRandomData != nil {
	n := copy(r, startupRandomData)
	extendRandom(r, n)
	return
	}
	fd := open(&urandom_dev[0], 0 /* O_RDONLY */, 0)
	n := read(fd, unsafe.Pointer(&r[0]), int32(len(r)))
	closefd(fd)
	extendRandom(r, int(n))
	}

	func goenvs() {
	goenvs_unix()
	}

	// Called to initialize a new m (including the bootstrap m).
	// Called on the parent thread (main thread in case of bootstrap), can allocate memory.
	func mpreinit(mp *m) {
	mp.gsignal = malg(32 * 1024) // Linux wants >= 2K
	mp.gsignal.m = mp
	}

	func msigsave(mp *m) {
	smask := (*sigset)(unsafe.Pointer(&mp.sigmask))
	if unsafe.Sizeof(*smask) > unsafe.Sizeof(mp.sigmask) {
	throw("insufficient storage for signal mask")
	}
	rtsigprocmask(_SIG_SETMASK, nil, smask, int32(unsafe.Sizeof(*smask)))
	}

	// Called to initialize a new m (including the bootstrap m).
	// Called on the new thread, can not allocate memory.
	func minit() {
	// Initialize signal handling.
	_g_ := getg()
	signalstack((byte)(unsafe.Pointer(_g_.m.gsignal.stack.lo)), 321024)

	// restore signal mask from m.sigmask and unblock essential signals
	nmask := (sigset)(unsafe.Pointer(&_g_.m.sigmask))
	for i := range sigtable {
	if sigtable[i].flags&_SigUnblock != 0 {
	nmask[(i-1)/32] &^= 1 << ((uint32(i) - 1) & 31)
	}
	}
	rtsigprocmask(_SIG_SETMASK, &nmask, nil, int32(unsafe.Sizeof(nmask)))
	}

	// Called from dropm to undo the effect of an minit.
	func unminit() {
	_g_ := getg()
	smask := (*sigset)(unsafe.Pointer(&_g_.m.sigmask))
	rtsigprocmask(_SIG_SETMASK, smask, nil, int32(unsafe.Sizeof(*smask)))
	signalstack(nil, 0)
	}

	func memlimit() uintptr {
	/*
	TODO: Convert to Go when something actually uses the result.

	Rlimit rl;
	extern byte runtime·text[], runtime·end[];
	uintptr used;

	if(runtime·getrlimit(RLIMIT_AS, &rl) != 0)
	return 0;
	if(rl.rlim_cur >= 0x7fffffff)
	return 0;

	// Estimate our VM footprint excluding the heap.
	// Not an exact science: use size of binary plus
	// some room for thread stacks.
	used = runtime·end - runtime·text + (64<<20);
	if(used >= rl.rlim_cur)
	return 0;

	// If there's not at least 16 MB left, we're probably
	// not going to be able to do much. Treat as no limit.
	rl.rlim_cur -= used;
	if(rl.rlim_cur < (16<<20))
	return 0;

	return rl.rlim_cur - used;
	*/

	return 0
	}

	//#ifdef GOARCH_386
	//#define sa_handler k_sa_handler
	//#endif

	func sigreturn()
	func sigtramp()

	func setsig(i int32, fn uintptr, restart bool) {
	var sa sigactiont
	memclr(unsafe.Pointer(&sa), unsafe.Sizeof(sa))
	sa.sa_flags = _SA_SIGINFO \| _SA_ONSTACK \| _SA_RESTORER
	if restart {
	sa.sa_flags \|= _SA_RESTART
	}
	sa.sa_mask = ^uint64(0)
	// Although Linux manpage says "sa_restorer element is obsolete and
	// should not be used". x86_64 kernel requires it. Only use it on
	// x86.
	if GOARCH == "386" \|\| GOARCH == "amd64" {
	sa.sa_restorer = funcPC(sigreturn)
	}
	if fn == funcPC(sighandler) {
	fn = funcPC(sigtramp)
	}
	sa.sa_handler = fn
	if rt_sigaction(uintptr(i), &sa, nil, unsafe.Sizeof(sa.sa_mask)) != 0 {
	throw("rt_sigaction failure")
	}
	}

	func setsigstack(i int32) {
	var sa sigactiont
	if rt_sigaction(uintptr(i), nil, &sa, unsafe.Sizeof(sa.sa_mask)) != 0 {
	throw("rt_sigaction failure")
	}
	if sa.sa_handler == 0 \|\| sa.sa_handler == _SIG_DFL \|\| sa.sa_handler == _SIG_IGN \|\| sa.sa_flags&_SA_ONSTACK != 0 {
	return
	}
	sa.sa_flags \|= _SA_ONSTACK
	if rt_sigaction(uintptr(i), &sa, nil, unsafe.Sizeof(sa.sa_mask)) != 0 {
	throw("rt_sigaction failure")
	}
	}

	func getsig(i int32) uintptr {
	var sa sigactiont

	memclr(unsafe.Pointer(&sa), unsafe.Sizeof(sa))
	if rt_sigaction(uintptr(i), nil, &sa, unsafe.Sizeof(sa.sa_mask)) != 0 {
	throw("rt_sigaction read failure")
	}
	if sa.sa_handler == funcPC(sigtramp) {
	return funcPC(sighandler)
	}
	return sa.sa_handler
	}

	func signalstack(p *byte, n int32) {
	var st sigaltstackt
	st.ss_sp = p
	st.ss_size = uintptr(n)
	st.ss_flags = 0
	if p == nil {
	st.ss_flags = _SS_DISABLE
	}
	sigaltstack(&st, nil)
	}

	func updatesigmask(m sigmask) {
	var mask sigset
	copy(mask[:], m[:])
	rtsigprocmask(_SIG_SETMASK, &mask, nil, int32(unsafe.Sizeof(mask)))
	}